From ccd7a7db10457ea7feaf677077b8b7e4c4da6366 Mon Sep 17 00:00:00 2001 From: Jeff Law Date: Wed, 13 Apr 1994 22:02:52 +0000 Subject: [PATCH] * config/pa/nm-hppab.h (STOPPED_BY_WATCHPOINT): Define. (HAVE_STEPPABLE_WATCHPOINT): Define. (TARGET_CAN_USE_HARDWARE_WATCHPOINT): Define. (target_{insert,delete}_watchpoint): Define. --- gdb/config/pa/nm-hppab.h | 68 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) diff --git a/gdb/config/pa/nm-hppab.h b/gdb/config/pa/nm-hppab.h index 8a615e8401b..c14cb255560 100644 --- a/gdb/config/pa/nm-hppab.h +++ b/gdb/config/pa/nm-hppab.h @@ -38,3 +38,71 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ target process... Which really pisses off GDB.) */ #define ATTACH_DETACH + +/* The PA-BSD kernel has support for using the data memory break bit + to implement fast watchpoints. + + Watchpoints on the PA act much like traditional page protection + schemes, but with some notable differences. + + First, a special bit in the page table entry is used to cause + a trap when a specific page is written to. This avoids having + to overload watchpoints on the page protection bits. This makes + it possible for the kernel to easily decide if a trap was caused + by a watchpoint or by the user writing to protected memory and can + signal the user program differently in each case. + + Second, the PA has a bit in the processor status word which causes + data memory breakpoints (aka watchpoints) to be disabled for a single + instruction. This bit can be used to avoid the overhead of unprotecting + and reprotecting pages when it becomes necessary to step over a watchpoint. + + + When the kernel receives a trap indicating a write to a page which + is being watched, the kernel performs a couple of simple actions. First + is sets the magic "disable memory breakpoint" bit in the processor + status word, it then sends a SIGTRAP to the process which caused the + trap. + + GDB will take control and catch the signal for the inferior. GDB then + examines the PSW-X bit to determine if the SIGTRAP was caused by a + watchpoint firing. If so GDB single steps the inferior over the + instruction which caused the watchpoint to trigger (note because the + kernel disabled the data memory break bit for one instruction no trap + will be taken!). GDB will then determines the appropriate action to + take. (this may include restarting the inferior if the watchpoint + fired because of a write to an address on the same page as a watchpoint, + but no write to the watched address occured). */ + +/* The PA can watch any number of locations, there's no need for it to reject + anything (generic routines already check that all intermediates are + in memory). */ +#define TARGET_CAN_USE_HARDWARE_WATCHPOINT(B) 1 + +/* When a hardware watchpoint fires off the PC will be left at the + instruction which caused the watchpoint. It will be necessary for + GDB to step over the watchpoint. + + On a PA running BSD, it is trivial to identify when it will be + necessary to step over a hardware watchpoint as we can examine + the PSW-X bit. If the bit is on, then we trapped because of a + watchpoint, else we trapped for some other reason. */ +#define STOPPED_BY_WATCHPOINT(W) \ + ((W).kind == TARGET_WAITKIND_STOPPED \ + && (W).value.sig == TARGET_SIGNAL_TRAP \ + && ((int) read_register (IPSW_REGNUM) & 0x00100000)) + +/* The PA can single step over a watchpoint if the kernel has set the + "X" bit in the processor status word (disable data memory breakpoint + for one instruction). + + The kernel will always set this bit before notifying the inferior + that it hit a watchpoint. Thus, the inferior can single step over + the instruction which caused the watchpoint to fire. This avoids + the traditional need to disable the watchpoint, step the inferior, + then enable the watchpoint again. */ +#define HAVE_STEPPABLE_WATCHPOINT + +/* Use these macros for watchpoint insertion/deletion. */ +#define target_insert_watchpoint(addr, len) hppa_set_watchpoint (addr, len, 1) +#define target_remove_watchpoint(addr, len) hppa_set_watchpoint (addr, len, 0) -- 2.30.2